On April 16, 2007, at 1730 central daylight time, an amateur-built Browns Vans RV-7A, N799WB, piloted by a private pilot, was substantially damaged during a forced landing following a loss of engine power while in cruise flight near Gardner, Illinois. Visual meteorological conditions prevailed at the time of the accident. The flight was operating under the provisions of 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The pilot reported minor injuries. The local area flight departed Lewis University Airport (LOT), Romeoville, Illinois, at 1700. The purpose of the accident flight was to verify the operation of navigational equipment with the use of the airplane's autopilot system. Prior to departure, the pilot completed an engine run-up and successfully tested both engine control units (ECUs). After departure, the pilot waited until leveling-off at 6,500 feet mean sea level (msl) to evaluate the navigational equipment. According to the pilot, the engine "suddenly lost power and started running rough" while in cruise flight. The pilot remembered hearing a "loud bang" when the engine lost power. The pilot set the propeller to low pitch and manipulated the engine throttle without any noticeable effect on engine operation. The engine continued to run "rough" after he switched fuel tanks. The pilot diverted toward Dwight Airport (DTG), which was about 9 nautical miles (nm) northeast of his position. When the airplane was at 2,500 feet msl, about 6 nm from DTG, the pilot elected to perform an off-field landing on a "narrow gravel lane with rough surface and significant potholes." The landing was made "downwind [and] without flaps." During the landing rollout the airplane departed off the left side of the road and flipped over in the adjacent ditch. The engine was a Mattituck TMX IOF-360, serial number 32744-1. The engine was equipped with an Aerosance PowerLink full authority digital engine control (FADEC) system. The FADEC system was powered-on prior to engine removal and no anomalies were noted during the system's startup diagnostic tests. The engine and its corresponding FADEC components were shipped to the manufacturer for additional testing. The engine started without hesitation and ran at various power settings for approximately 25 minutes. Proper engine operation was demonstrated with both ECUs running simultaneously, as well as independent of each other. The engine demonstrated normal operation throughout its entire rpm/horsepower range. Engine rpm was cycled rapidly between flight idle and maximum continuous rpm several times without any hesitation in engine operation. No anomalies were noted during the engine test run that would have prevented its normal operation. At departure, the airplane reportedly had 38 gallons of 100 low lead aviation fuel onboard. Examination of the wreckage confirmed there was sufficient fuel available for engine operation, and there was fuel found in the line from the fuselage to the mechanical fuel pump.